Now I'd like to switch gears and
address another novel concept that
has originated based on
work in our laboratory.
The basic premise here is that some
elements of inducible wound healing
is actually retained in the adult
skin tissue in a silenced form.
This silencing is primarily
executed by microRNA.
As one example, we have
discovered that miR-200b in skin,
microvascular endothelial cells,
act as an angiostatic agent
This silencer is
wound angiogenesis to start.
Let's look at the data here.
In Panel A, you see human
microvascular dermal endothelial
cells, a scratch assay
has been done to study
the migration of these cells.
And if you added miR-200b
mimic to these cells
you clearly blunt or decelerate
the migration of the cells
across the scratch.
In Panel B, it is shown that
the ability of these cells
to from tubes in a matrigel, which
is a sign of angiogenic property,
such angiogenic property is
remarkably blunted or impaired
in the presence of miR-200b mimic.
Supporting the notion that miR-200b
has potent angiostatic properties.
In the intact adult skin,
it is critically important
to keep angiogenesis under check.
And miR-200b is one such silencer
that contains angiogenic response
under intact skin conditions.
Following wounding, however,
miR-200b levels in the skin
sharply go down.
In Panel A, we see that following 3
days after wounding miR-200b levels
in the wound edge tissue
is significantly lower.
And as the wound heals,
miR-200b comes up,
and the expectation here is that
this rebound of miR-200b expression
is aimed at restoring
homeostasis in the skin,
meaning stopping unwanted
after the wound has closed.
Now this lowering of
miR-200b following wounding,
as noted in the wound test tissue
in Panel A, what are the cell
types primarily responsible
for this type of lowering?
The answer to that question,
the wound test tissue was taken,
and endothelial cells
were laser captured
from that wound test issue.
And the results, as
shown in Panel B,
demonstrate that specifically
endothelial cell, microRNA-200b, is
To test the significance of
miR-200b in wound angiogenesis,
we sought to deliver the
miR-200b gene to the skin.
As you see in Panel A, the
lentiviral gene delivery process
resulted in almost doubling of the
expression of 200b in the skin.
Following such successful
delivery of miR-200b to the skin,
the skin was then wounded and
angiogenic outcomes, such as blood
flow and endothelial cell
density, was enumerated.
Panel B shows that 7 days
after wounding the skin that
was subjected to over
expression of miR-200b,
blood flow in the skin
affected by the wound
was substantially lower in response
to miR-200b over expression.
Similarly, it was noted that CD
31 positive endothelial cell count
in the wound test tissue was
also significantly lower.
Suggesting that miR-200b
does play an important role
angiogenesis in the skin.
Diabetic wounds are subjected
to a number of complications.
Of which, one critical factor
is excessive inflammation.
We have demonstrated that high
TNF levels during this condition
of excessive inflammation
associated with diabetic wounds,
resist the lowering of
miR-200b following wounding.
As a result, even after wounding,
miR-200b levels stay high.
And that is one factor that impairs
diabetic wound angiogenesis.
We have also reported
this additional or excessive
TNF alpha in the diabetic wound,
helps bring down the miR-200b.
As those of the which, wound
angiogenesis may be jump started.
Let us look at some of the data.